Mr-angiography with non-cartesian signal acquisition

Abstract

In a method and apparatus for the creation of an MR image of a vascular structure of an examination region, the spins in the examination region are saturated by the irradiation of at least one RF saturation signal, which delivers a lower signal intensity as spins in a subsequent MR signal recording for the creation of the MR angiographic image, which flow through at least one blood vessel into the examination region, and are not saturated by the RF saturation pulse. Raw data space of the MR angiographic image is read out with a non-Cartesian trajectory in the MR signal acquisition for the creation of the MR angiographic image.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention concerns a method for the generation of an MR image of a vascular structure of an examination region, and an MR apparatus for this purpose. In the following, the term “angiography image” shall be used in the generic sense; it does not necessarily encompass only a single two-dimensional image, but depending on the context, may also encompass an angiographic image data set of a desired volume.[0003]2. Description of the Prior Art[0004]In the field of MR angiography, methods that function without the need for contrast agents are gaining significance. One class of such methods exploits the pulsatile nature of the arterial blood flow. With signal recording (data acquisition) of a flow-sensitive sequence at the point in time of the quicker flow rate (systole), one obtains, in the ideal case, a deletion (absence) of the arterial signal. With a signal recording at the point in time in the cardiac cycle at ...

AI Technical Summary

Benefits of technology

The present invention provides an angiography method that can obtain high-quality images quickly. The method uses an irregular distribution of spokes in the image to create an elliptical or oval field of view, which allows for optimized adjustment to the object being depicted. In addition, a suppression of the fat signal during the signal recording is performed to reduce interference from potential fatty tissues. The density of the spokes can also be decreased in certain partitions to improve image quality.

Problems solved by technology

A fundamental problem with this method is that the vessels of the volume in question must be filled during tin with fresh blood, flowing in from outside of the marked volume.

This limitation is more striking with patients whose pulsatile dynamics are less pronounced, wherein the distance traveled by the blood during the remaining weak pulse wave may be significantly shorter.

To create thinner thicknesses, an extension of the RF pulse, and thus the repetition periods TR, is required, which is undesired.

Furthermore, with even thinner layers, the obtainable signal-to-noise ratio is marginally low, in particular with the clinically, currently most commonly used, field strengths of 1.5 tesla.

This spatial resolution, limited in the z-axis, represents a major limitation of the method, in particular when finer vessels do not run strictly along the z-axis, as is the case, for example, in regions of the trifurcation in the lower leg, or with pathologies.

A problem with this alternative would be that efficiency would not be increased because the time for encoding a 3D partition is the same as that for the acquisition of a 2D layer.

This is a problem, because, for example, with an angiography of the pelvis-leg region, normally a coverage from the feet up to the abdominal region is desired.

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